Search

Mining activities can cause adverse and long-lasting environmental impacts and detailed monitoring is therefore essential to assess the pollution status of mining impacted areas. Here we evaluated the efficacy of two predatory fish species (Gadus ogac i.e. Greenland cod and Myoxocephalus scorpius i.e. shorthorn sculpin) as biomonitors of mining derived metals (Pb, Zn, Cd and Hg) by measuring concentrations in blood, liver, muscle and otoliths along a distance gradient near the former Black Angel Pb-Zn mine (West Greenland). We detected metals in all tissues (except Cd and Hg in otoliths) and sculpin generally displayed higher concentrations than cod. For both species, concentrations were generally highest closest to the dominant pollution source(s) and gradually decreased away from the mine. The clearest gradient was observed for Pb in blood and liver (both species), and for Pb in otoliths (sculpin only). Similar to dissolved concentrations in seawater (but in contrast to bottom sediment), no significant decrease was found for Zn, Cd and Hg in any of the tissues. This demonstrates that by including tissues of blood (representing recent accumulation) and otolith (representing more long-term exposure signals) in the sampling collection, the temporal information on contaminant exposure and accumulation can be extended. We therefore conclude that both fish species are suitable as biomonitors near Arctic mine sites and, moreover, that blood and otoliths can serve as important supplementary monitoring tissues (in addition to liver and muscle traditionally sampled) as they provide extended temporal information on recent to long-term contaminant exposure., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The inappropriate and unsafe management practices related to disposal and recycling of electronic wastes in Nigeria has led to environmental and underground water contamination. Reports on the level and type of contamination as well as the possible DNA damage effects of this contamination are insufficient. This study evaluated the DNA damaging potential of e-waste simulated and raw leachates, and its contaminated underground water using the SOS chromotest on Escherichia coli PQ37 and the Ames Salmonella fluctuation test on Salmonella typhimurium strains TA98 and TA100, without and with metabolic activation. Physico-chemical parameters of the samples were also analyzed. The result of the Ames test showed induction of base pair substitution and frameshift mutation by the test samples. However, the TA100 was the more responsive strain for the three samples in terms of mutagenic index in the absence and presence of metabolic activation. The SOS chromotest results were in agreement with those of the Ames Salmonella fluctuation test. Nevertheless, the E. coli PQ37 system was slightly more sensitive than the Salmonella assay for detecting genotoxins in the tested samples. Lead, cadmium, manganese, copper, nickel, chromium, arsenic, and zinc contents analyzed in the samples were believed to play a significant role in the observed DNA damage in the microbial assays. The results of this study showed that e-waste simulated and raw leachates, and its contaminated underground water are of potential mutagenic and genotoxic risks to the exposed human populace.

A physiologically based pharmacokinetic (PBPK) model for hexavalent chromium [Cr(VI)] in mice, rats, and humans developed previously (Kirman et al., 2012, 2013), was updated to reflect an improved understanding of the toxicokinetics of the gastrointestinal tract following oral exposures. Improvements were made to: (1) the reduction model, which describes the pH-dependent reduction of Cr(VI) to Cr(III) in the gastrointestinal tract under both fasted and fed states; (2) drinking water pattern simulations, to better describe dosimetry in rodents under the conditions of the NTP cancer bioassay; and (3) parameterize the model to characterize potentially sensitive human populations. Important species differences, sources of non-linear toxicokinetics, and human variation are identified and discussed within the context of human health risk assessment., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

The present study reports metal and arsenic contamination in sediments, as well as element accumulation and partitioning in the polychaete Diopatra neapolitana in the Ria de Aveiro lagoon (Portugal). The polychaetes biochemical performance and tissue regenerative capacity were also evaluated. The concentration of elements in sediments showed an increase of contamination among areas (areas A-G), but higher bioaccumulation was observed in organisms from a less contaminated area (area C, BAF>1). This study evidenced that individuals with higher elements bioaccumulation presented higher LPO and lower GSH/GSSG and also exhibited lower capacity for body regeneration. Polychaetes biotransformation capacity as well as antioxidant defense mechanisms were not sufficiently efficient to withstand the excess of ROS leading to increased LPO when organisms presented higher bioaccumulation levels. Additionally, an increase of methalotionines was also observed in individuals with higher bioaccumulation of metals and As, suggesting an induction of detoxification processes., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Effect of cadmium cations and their interaction with silicon cations was determined in poplar calli and expressed as changes in callus growth, cell viability and cadmium cation accumulation. Cell viability throughout culture versus cadmium cation accumulation in cells is discussed. At the same time, the study sought appropriate methods for cadmium cation detection in callus cells and also in experiments with low plant material (e.g. protoplasts). Cadmium cations were determined by atomic absorption spectroscopy and using fluorescence microscopy with a specific cadmium cation fluorescent dye. The detection of cadmium cations in callus cells by the latter method appears suitable because the callus cells are surrounded by primary cell walls without auto-fluorescence and these values fit well with atomic absorption spectroscopy quantification. However, the visualisation method has some limits discussed below.

The neurotoxicity of methylmercury (MeHg) is well characterised, and the ameliorating effects of selenium have been described. However, little is known about the molecular mechanisms behind this contaminant-nutrient interaction. We investigated the influence of selenium (as selenomethionine, SeMet) and MeHg on mercury accumulation and protein expression in the brain of adult zebrafish ( Danio rerio ). Fish were fed diets containing elevated levels of MeHg and/or SeMet in a 2 × 2 full factorial design for eight weeks. Mercury concentrations were highest in the brain tissue of MeHg-exposed fish compared to the controls, whereas lower levels of mercury were found in the brain of zebrafish fed both MeHg and SeMet compared with the fish fed MeHg alone. The expression levels of proteins associated with gap junction signalling, oxidative phosphorylation, and mitochondrial dysfunction were significantly ( p < 0.05) altered in the brain of zebrafish after exposure to MeHg and SeMet alone or in combination. Analysis of upstream regulators indicated that these changes were linked to the mammalian target of rapamycin (mTOR) pathways, which were activated by MeHg and inhibited by SeMet, possibly through a reactive oxygen species mediated differential activation of RICTOR, the rapamycin-insensitive binding partner of mTOR.

The environmental fate of metazachlor herbicide was investigated under field conditions in rapeseed cultivated and uncultivated plots, over a period of 225 days. The cultivation was carried out in silty clay soil plots with two surface slopes, 1 and 5 %. The herbicide was detectable in soil up to 170 days after application (DAA), while the dissipation rate was best described by first-order kinetics and its half-life ranged between 10.92 and 12.68 days. The herbicide was detected in the soil layer of 10-20 cm from 5 to 48 DAA, and its vertical movement can be described by the continuous stirred tank reactor (CSTR) in series model. Relatively low amounts of metazachlor (less than 0.31 % of the initial applied active ingredient) were transferred by runoff water. More than 80 % of the total losses were transferred at the first runoff event (12 DAA), with herbicide concentrations in runoff water ranging between 70.14 and 79.67 μg L -1 . Minor amounts of the herbicide (less than 0.07 % of the initial applied active ingredient) were transferred by the sediment, with a maximum concentration of 0.57 μg g -1 (12 DAA), in plots with 5 % inclination. Finally, in rapeseed plants, metazachlor was detected only in the first sampling (28 DAA) at concentrations slightly higher than the limit of quantification; when in seeds, no residues of the herbicide were detected.

Recent studies evidence that macrophytes can uptake and bioaccumulate microcystins (MC) from contaminated environments, suggesting their use in phytoremediation. In the present study Ceratophyllum demersum, Egeria densa and Hydrilla verticillata were exposed to cell free crude extracts (CE) containing three MC congeners MC-LR, MC-RR and MC-YR at a total MC concentration of 104.4 ± 7.6 μg/L from Lake Amatitlán, Guatemala. Time dependent total glutathione (tGSH), glutathione disulfide (GSSG), disappearance of MC from exposure medium and macrophyte uptake as well as calculated uptake and biotransformation rates and bioconcentration factors (BCF) were monitored after 1, 4, 8 hours (h) and 1, 3, 7 and 14 days (d). Results showed that tGSH concentrations in all exposed macrophytes were enhanced by CE. Disappearance of 62.1 ± 13, 40.8 ± 3.1 and 37.8 ± 3.5 μg/L total MCs from exposure mediums with E. densa, H. verticillata and C. demersum were observed after 1 h. Followed by the total elimination of MCs in exposure medium from H. verticillata after 14 d. Highest MC bioaccumulation capacity (BCF), was observed in E. densa followed by C. demersum and H. verticillata. The here presented results imply the strong MC phytoremediation potential of the evaluated macrophytes., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The Aleutian Archipelago is an isolated arc of over 300 volcanic islands stretching 1,600 km across the interface of the Bering Sea and North Pacific Ocean. Although remote, some Aleutian Islands were heavily impacted by military activities from World War II until recently and were exposed to anthropogenic contaminants, including mercury (Hg). Mercury is also delivered to these islands via global atmospheric transport, prevailing ocean currents, and biotransport by migratory species. Mercury contamination of freshwater ecosystems is poorly understood in this region. Total Hg (THg) concentrations were measured in threespine stickleback fish (Gasterosteus aculeatus) collected from eight lakes at Adak Island, an island in the center of the archipelago with a long military history. Mean THg concentrations for fish whole-body homogenates for all lakes ranged from 0.314 to 0.560 mg/kg dry weight. Stickleback collected from seabird-associated lakes had significantly higher concentrations of THg compared to non-seabird lakes, including all military lakes. The δ(13)C stable isotope ratios of stickleback collected from seabird lakes suggest an input of marine-derived nutrients and/or marine-derived Hg., (Copyright © 2012 SETAC.)

Unlabelled: Levels and profiles of 10 individual congeners of polychlorinated biphenyls (PCBs) were studied in 3 species of commercial scallops (Pecten maximus, Chlamys varia, and Chlamys opercularis) from several Rías in Galician littoral (NW, Spain). ΣPCBs levels ranged from 2.21 to 41.0 ng/g wet weight for P. maximus, from 13.9 to 24.9 ng/g wet weight for C. varia, and from 1.58 to 24.3 ng/g wet weight for C. opercularis. The possible influence between biometric parameters (lipid content, condition index, and shell size) and PCBs levels were studied using statistical analysis (ANOVA). No relationship between biometric parameters could be established in the studied samples. Multivariate analysis showed there were differences in bioaccumulation of some PCBs congeners. Principal component analysis classifies clearly the 3 studied Rías (Ría de Ferrol, Ría de Arousa, and Ría de Vigo) taking into account PCBs levels found in the shellfish., Practical Applications: We investigated levels and profiles of 10 congeners of PCBs in 3 commercial scallop species from the Galician littoral zone. The influence of 3 biometric parameters on polychlorinated biphenyls (PCBs) levels was also studied in order to assess results from the monitoring programs of production areas. According to PCBs levels, geographical differences were observed in commercial scallops from the 3 studied estuarine bays (Ría de Ferrol, Ría de Arousa, and Ría de Vigo)., (© 2012 Institute of Food Technologists®)

Consumption of periphyton is a potentially important route of metal exposure to benthic invertebrate grazers. The present study examined the bioaccumulation kinetics of dissolved and dietary Cd and Cu in five species of mayflies (class Insecta). Artificial stream water and benthic diatoms were separately labeled with enriched stable metal isotopes to determine physiological rate constants used by a biokinetic bioaccumulation model. The model was employed to simulate the effects of metal partitioning between water and food, expressed as the bioconcentration factor (BCF), as well as ingestion rate (IR) and metal assimilation efficiency of food (AE), on the relative importance of water and food to metal bioaccumulation. For all test species, the contribution of dietary uptake of Cd and Cu increased with BCF. For a given BCF, the contribution of food to the body burden increased with k(uf) , the metal uptake rate constant from food that combined variation in IR and AE. To explore the relative importance of water and diet exposure routes under field conditions, we used estimated site-specific aqueous free-ion concentrations to model Cd and Cu accumulation from aqueous exposure, exclusively. The predicted concentrations accounted for less than 5% of the observed concentrations, implying that most bioaccumulated metal was acquired from food. At least for the taxa considered in this study, we conclude that consumption of metal-contaminated periphyton can result in elevated metal body burdens and potentially increase the risk of metal toxicity., (Copyright © 2011 SETAC.)

The objective of the present study was to describe the uptake and elimination kinetics of selenium (Se) administered in the forms of selenate, selenite, and selenomethionine (seleno-DL-methionine) in different life stages of the midge Chironomus dilutus, and to determine the relationship between Se bioavailability and Se speciation using X-ray absorption spectroscopy (XAS). Midge larvae exposed to 4.3 µg/L as dissolved selenate for 10 d of had negligible accumulation of Se (indistinguishable from control organisms). However, larvae rapidly accumulated Se over 10 d of exposure to 3.8 and 1.8 µg/L selenite and seleno-DL-methionine (Se-met), respectively. Most Se accumulated by larvae exposed to selenite or Se-met was retained after 10 d of elimination in clean water. When additional midge larvae were exposed to Se until emergence, Se accumulated during the larval stage was largely retained in the adults. Although a strong correlation was found between the adult whole-body Se concentration and the Se concentration in the exuvia after emergence, only a minor loss of Se occurred in the shed exuvia compared with larvae and adult whole-body concentrations. X-ray absorption spectroscopy analysis showed that organic selenides and diselenides, modeled as Se-met and selenocystine, respectively, were the dominant forms of Se in both the larval and adult insect stages. The proportion and concentration of organic selenides (selenomethionine) increased in larvae and adults exposed to Se-met and selenite compared with larvae exposed to selenate, whereas the concentration of diselenides (selenocystine) remained relatively constant for all treatments., (Copyright © 2011 SETAC.)

The traditional approach for predicting the risk of hydrophobic organic contaminants (HOCs) in sediment is to relate organic carbon normalized sediment concentrations to body residues or toxic effects to organisms. However, due to the multiple variables controlling bioavailability, this method has limitations. A matrix independent method of predicting bioavailability needs to be used in order to be universally applicable. Both chemical activity (freely dissolved chemical concentrations) measured by solid-phase microextraction (SPME) and bioaccessibility (rapidly desorbing fraction) estimated by Tenax extraction have been developed to predict bioavailability of sediment-associated HOCs. The objectives of this review are to summarize a number of studies using matrix-SPME or Tenax extraction to estimate bioavailability and/or toxicity of different classes of HOCs and evaluate the strengths and weakness of these two techniques. Although the two chemical techniques assess different components of the matrix, estimates obtained from both techniques have been correlated to organism body residues. The advantages of SPME fibers are their applicability for use in situ and their potential usage for a wide array of contaminants by selection of appropriate coatings. Single time-point Tenax extraction, however, is more time- and labor-effective. Tenax extraction also has lower detection limits, making it more applicable for highly toxic contaminants. This review also calls for additional research to evaluate the role of sequestrated contaminants and ingestion of sediment particles by organisms on HOC bioavailability. The use of performance reference compounds to reduce SPME sampling time and linking chemical based bioavailability estimates to toxicological endpoints are essential to expand the applications of these methods.

As part of a SETAC Pellston Workshop, we evaluated the potential use of metal tissue residues for predicting effects in aquatic organisms. This evaluation included consideration of different conceptual models and then development of several case studies on how tissue residues might be applied for metals, assessing the strengths and weaknesses of these different approaches. We further developed a new conceptual model in which metal tissue concentrations from metal-accumulating organisms (principally invertebrates) that are relatively insensitive to metal toxicity could be used as predictors of effects in metal-sensitive taxa that typically do not accumulate metals to a significant degree. Overall, we conclude that the use of tissue residue assessment for metals other than organometals has not led to the development of a generalized approach as in the case of organic substances. Species-specific and site-specific approaches have been developed for one or more metals (e.g., Ni). The use of gill tissue residues within the biotic ligand model is another successful application. Aquatic organisms contain a diverse array of homeostatic mechanisms that are both metal- and species-specific. As a result, use of whole-body measurements (and often specific organs) for metals does not lead to a defensible position regarding risk to the organism. Rather, we suggest that in the short term, with sufficient validation, species- and site-specific approaches for metals can be developed. In the longer term it may be possible to use metal-accumulating species to predict toxicity to metal-sensitive species with appropriate field validation., (Copyright © 2010 SETAC.)

Multivariate analysis including correlation, multiple stepwise linear regression, and cluster analyses were applied to investigate the heavy metal concentrations (Cd, Cu, Fe, Ni, Pb, and Zn) in the different parts of bivalves and gastropods. It was also aimed to distinguish statistically the differences between the marine bivalves and the gastropods with regards to the accumulation of heavy metals in the different tissues. The different parts of four species of bivalves and four species of gastropods were obtained and analyzed for heavy metals. The multivariate analyses were then applied on the data. From the multivariate analyses conducted, there were correlations found between the soft tissues of bivalves and gastropods, but none was found between the shells and the soft tissues of most of the molluscs (except for Cerithidea obtusa and Puglina cochlidium). The significant correlations (P < 0.05) found between the soft tissues were further complemented by the multiple stepwise linear regressions where heavy metals in the total soft tissues were influenced by the accumulation in the different types of soft tissues. The present study found that the distributions of heavy metals in the different parts of molluscs were related to their feeding habits and living habitats. The statistical approaches proposed in this study are recommended for use in biomonitoring studies, since multivariate analyses can reduce the cost and time involved in identifying an effective tissue to monitor the heavy metal(s) bioavailability and contamination in tropical coastal waters.

In this study, the mercury (Hg) removal capacities of two aquatic macrophytes, Pistia stratiotes and Azolla pinnata, were investigated against the coal mining effluent. These plants reduced mercury from the effluent via rhizofiltration and subsequent accumulation in plant. The removal rate of P. stratiotes and A. pinnata was 80% and 68%, respectively, after 21 days of exposure to the effluent containing 10 microg L(-1) of Hg. As mercury from the effluent was accumulated in the root and shoot tissues of both aquatic macrophytes, they were proven to be a root accumulator with a translocation factor of less than one during the entire study. The decreasing Hg content in effluent (from 10 to 2.0 microg L(-1)) was reflected by its accumulation in roots (0.57+/-0.02 mg g(-1) in P. stratiotes) and leaves of the experimental plants (0.42+/-0.01 mg g(-1), P. stratiotes). As a result, Hg concentrations in the coal mining effluent were tightly associated with those observed from macrophytes. Considering the high removal efficiencies of Hg by these aquatic macrophytes, these plants can be recommended for the actual treatment of Hg-containing waste waters.

In order to clarify the role of metallothioneins (MT) in copper (Cu) toxicity, this work aimed to assess the involvement of this protein in the accumulation and elimination strategies of Cu in the clam Ruditapes decussatus exposed to two sublethal concentrations (25 and 50 microgCul(-1)). The behaviour of MT in three different tissues of clams during the accumulation and depuration processes was also followed by gel-filtration chromatography to assess if Cu was bound to MT or to other cytosolic components. The 96 h LC50 for water-borne copper was 715 microgL(-1) in R. decussatus. The Cu accumulation pattern was dependent on Cu exposure concentrations. In clams exposed to 25 microgl(-1), total Cu accumulation in the three tissues increased linearly during the exposure period, while in those exposed to 50 microgl(-1) it followed the first order kinetic model. The greatest amount of Cu accumulated in all tissues is associated to the low molecular weight cytosolic fraction (>50%). The chromatographic assay indicated that Cu in the cytosolic fraction is bound to MT and MT levels increase with the increase of Cu exposure confirming the binding affinity of Cu to MT in all tissues. However, a smaller percentage of Cu seems to be bond to other ligands, such as GSH. Copper was exponentially eliminated (only studied in clams exposed to 25 microgl(-1)) and the estimated half-life was tissue dependent (9, 5 and 14 days for the gills, digestive gland and remaining tissues, respectively). Copper bound to the thermostable compounds was eliminated more quickly (t(1/2)=4-7 days) in all tissues than those bound to the thermolabile compounds (t(1/2)=7-18 days). Interestingly, MT is rapidly degraded (t(1/2)=7 and 18 days), suggesting that this protein is actively involved in the elimination of this metal, through the Cu-MT complex since MT and Cu are turning over simultaneously. Therefore, when Cu exposure is low, the clam can cope efficiently with the excess of Cu levels by increasing MT induction as well as rapidly eliminating this metal via the MT-Cu complex. Copper toxicity in the clam R. decussatus is associated to the limited capacity of MT induction at higher and environmental unrealistic Cu exposures especially in the gills and remaining tissues.

The winter stress syndrome hypothesis proposes that the combination of winter conditions and contaminant exposure reduces overwinter survival in juvenile fishes, mainly due to increased depletion of stored energy (lipids). To test this hypothesis in the field, juvenile fathead minnows (Pimephales promelas), creek chub (Semotilus atromaculatus), and white sucker (Catostomus commersoni) were collected from three exposure sites along Junction Creek, Sudbury, Ontario, Canada, representing cumulative inputs from metal mining and municipal wastewater. Overwinter survival potential was determined through measurements of growth (length, weight, muscle RNA/DNA ratio, muscle proteins) and energy stores (whole body triglycerides) in fish collected just prior to and following the overwinter period. We hypothesized that fish collected from exposure sites would exhibit reduced growth and energy storage compared to reference fish in both fall and spring, and that fish from all sites would exhibit reduced energy storage in spring compared to the previous fall. Whole body Se concentrations were elevated (11-42 microg/g dry wt) in juvenile fathead minnows and white sucker collected at two exposure sites in comparison to fish collected from the reference site (3-6 microg/g dry wt). In contrast to our hypothesis, fathead minnows were larger with greater triglyceride stores at exposure sites compared to the reference site. White suckers were smaller at exposure sites but did not differ in triglycerides among sites. Overall, the results in these fish species exposed to metal mining and municipal wastewaters do not support the winter stress syndrome hypothesis. It is recommended that future studies focus on relating growth and energy storage with other environmental factors such as habitat and food availability in addition to anthropogenic contamination.

The root uptake of lead (Pb) by trees and the transfer of Pb by leaf litter deposition to the forest floor were investigated through a pot experiment with Norway spruce. Natural Pb and radio isotopic lead (210Pb) were determined in needles and twigs and in the pot soil spiked with 210Pb. Calculations of the specific activity in plant material and in the supporting pot soil showed that less than 2% of the Pb content of needles and twigs originates from root uptake and approximately 98% are deposited from the atmosphere. Atmospheric Pb has declined by a factor of 7 from 1980 to 2007 but is still a major pathway of Pb to vegetation and topsoils. The conclusion from the experiment is that the internal circulation of Pb through root uptake, translocation and litterfall, gives an insignificant input of Pb to the forest floor compared to atmospheric deposition.

The purpose of this study was to evaluate the level of heavy metal contamination of perch (Perca fluviatilis) from inland waters in Latvia. The level of metal (Cd, Cu, Co, Pb, Ni, Mn, Zn, Fe) accumulation in fish tissues (muscle, liver, and gills) relative to contamination level, gender, age, and tissue type were studied in fish samples from 14 bog (dystrophic) lakes and 23 lakes of different trophic status. Samples from some sites in the vicinity of the largest cities had significantly increased metal levels. In contrast, fish tissues from bog lakes had very low metal levels, possibly because of the high concentrations of natural organic matter in these waters.

The overall aim of this research project was to reduce low molecular weight hydrocarbons such as benzene in produced wastewaters. Over 30 months of research was conducted to test the treatment performance in terms of benzene removal in vertical-flow constructed wetlands. Based on an influent concentration of 1 g L(-1) benzene, the results show mean benzene removal efficiencies between 88.71% and 89.77%, and 72.66% and 80.46% for indoor and outdoor constructed wetlands, respectively. A statistical analysis indicated that the five days at 20 degrees C N-allylthiourea biochemical oxygen demand (BOD(5)), chemical oxygen demand (COD), nitrate-nitrogen (NO(3)-N), dissolved oxygen (DO) and electric conductivity (EC) values of the effluent were positively correlated with the effluent benzene concentrations following the order COD>DO>EC>NO(3)-N>BOD(5), and negatively correlated according to the order pH>redox potential (redox)>temperature (T)>turbidity. No strong relationships between benzene and the variables ortho-phosphate-phosphorus (PO(4)(3-)) and ammonia-nitrogen (NH(4)-N) were recorded.

Many floodplains contain high concentrations of sediment associated contaminants that might be subjected to large changes in terms of mobility, transformation and bioavailability. Therefore, this study describes 1) changes in the redox conditions and the mobility of metals in artificially uncovered polluted floodplain sediments, 2) metal uptake by organisms and 3) colonization, succession and functioning of benthic algae on these sediments. Flooding caused long term changes in redox potential (Eh) profiles. In top layers strong gradients in redox potential established quickly, while in deeper layers changes occurred more gradually. The availability of copper as measured by Diffusive Gradients in Thinfilms (DGT) showed a consistent relationship with fluctuations in Eh. However, this relationship was restricted to deeper layers in the sediment. Within 1 week high amounts of total copper were immobilized. Differences in total copper concentrations between polluted and clean sediments became only partially apparent when comparing the available copper fraction (DGT-Cu). Introduced Tubifex shows only marginal differences in levels of accumulated Cu. Colonization, growth and succession of algal communities on polluted sediments was not impaired, most likely due to low bioavailability. It is concluded that changing environmental conditions, such as flooding, can result in stable chemical conditions with low a availability of metals and hence in a diminution of actual ecological risks.

A rapid biological method for the determination of the bioavailability of naphthalene was developed and its value as an alternative to extraction-based chemical approaches demonstrated. Genetically engineered whole-cell biosensors are used to determine bioavailable naphthalene and their responses compared with results from Tenax extraction and chemical analysis. Results show a 1:1 correlation between biosensor results and chemical analyses for naphthalene-contaminated model materials and sediments, but the biosensor assay is much faster. This work demonstrates that biosensor technology can perform as well as standard chemical methods, though with some advantages including the inherent biological relevance of the response, rapid response time, and potential for field deployment. A survey of results from this work and the literature shows that bioavailability under non-equilibrium conditions nonetheless correlates well with K(oc) or K(d). A rationale is provided wherein chemical resistance is speculated to be operative.

The need to understand chemical uptake, distribution, and metabolism in embryonic and larval fish derives from the fact that these early life stages often exhibit greater sensitivity to xenobiotic compounds than do adult animals. In this study, a 6-h acute waterborne exposure immediately after fertilization was used to quickly load the egg with benzo[a]pyrene (BaP). This exposure was used to mimic the initial egg concentration of a persistent bioaccumulative toxicant that could result from maternal transfer. We used multiphoton laser scanning microscopy (MPLSM) in combination with conventional analytical chemistry methods to characterize the tissue distribution of BaP and its principal metabolites in medaka embryos and post-hatch larvae. Embryonic metabolism of BaP was evident by MPLSM prior to liver formation or heart development. A major product of this metabolism was identified by liquid chromatography/mass spectrometry as BaP-3-glucuronide. MPLSM showed that metabolites were sequestered within the yolk, biliary system, and gastrointestinal tract. When the gastrointestinal tract became patent a few days after hatch, the metabolites were rapidly eliminated. These findings indicate that some of the earliest embryonic tissues are metabolically competent and that redistribution of BaP and its metabolic products occurs throughout development. Rapid metabolism of BaP substantially reduces the body burden of parent chemical in the developing embryo, potentially reducing toxicity. It remains unclear whether metabolism of BaP in medaka embryos leads to the formation of DNA adducts associated with genotoxic effects or yields metabolites that later lead to other toxicity in juveniles or adults.

In this study, we attempted to treat groundwater contaminated with nitrate using a two-stage removal system: one is biological treatment using the nitrate-degrading bacteria Pseudomonas sp. RS-7 and the other is chemical treatment using a coagulant. For the biological system, the effect of carbon sources on nitrate removal was first investigated using mineral salt medium (MSM) containing 500 mg l(-1) nitrate to select the most effective carbon source. Among three carbon sources, namely, glucose, starch and cellulose, starch at 1% was found to be the most effective. Thus, starch was used as a representative carbon source for the remaining part of the biological treatment where nitrate removal was carried out for MSM solution and groundwater samples containing 500 mg l(-1) and 460 mg l(-1) nitrate, respectively. About 86% and 89% of nitrate were removed from the MSM solution and groundwater samples, respectively at 72 h. Chemical coagulants such as alum, lime and poly aluminium chloride were tested for the removal of nitrate remaining in the samples. Among the coagulants, lime at 150 mg l(-1) exhibited the highest nitrate removal efficiency with complete disappearance for the MSM solutions. Thus, a combined system of biological and chemical treatments was found to be more effective for the complete removal of nitrate from groundwater.

Pieces of gill isolated from the clam Mercenaria mercenaria clear colloidal graphite from seawater, and the clearance rates are measurable. 5-Hydroxytryptamine (5-HT) had a biphasic effect on clearance rates: concentrations from 10(-6) to 10(-5) mol l(-1) 5-HT increased clearance, but higher concentrations reduced it. During the summer, the gills were less responsive to 5-HT: the threshold increased from 1 x 10(-6) to 5 x 10(-6) mol l(-1), and although the rate was still maximal at 10(-5) mol l(-1), it was significantly lower than the maximal rate in the winter. At 10(-5) mol l(-1) 5-HT, which maximized clearance, the lateral cilia were active, the interfilament space decreased and the diameter of the water tubes increased. Higher concentrations of 5-HT contracted the gill musculature, which inhibited the lateral cilia, decreased the interfilament space even more and decreased the diameter of the water tubes. The nitric oxide (NO) generator DEANO stimulated clearance in the winter but had no effect during the summer. L-NAME, an inhibitor of NO synthesis, diminished the effect of 5-HT during the winter but was ineffective during the summer. The diminished response to 5-HT of winter gills treated with L-NAME was statistically equal to the response of the gills to 5-HT during the summer. Dopamine (DA) inhibited clearance, and the gills were more sensitive to DA in winter than in summer. Microscopic examination of untreated gills revealed little or no lateral ciliary activity, and clearance was minimal. Thus, clearance rates of isolated gills behave in a manner consistent with the seasonality and pharmacology of the lateral cilia and branchial musculature.

An in vitro gut sac technique was used to compare the uptake rates of essential (copper, zinc and nickel) and non-essential metals (silver, cadmium and lead) at 50 micromol L(-1) each (a typical nutritive level in solution in chyme) in the luminal saline in four sections of the gastro-intestinal tract (stomach, anterior, mid and posterior intestines) of the freshwater rainbow trout. Cu, Zn, Cd and Ag exhibited similar regional patterns: on an area-specific basis, uptake rates for these metals were highest in the anterior intestine, lowest in the stomach, and approximately equal in the mid and posterior intestinal segments. When these rates were converted to a whole animal basis, the predominance of the anterior intestine increased because of its greater area, while the contribution of the stomach rose slightly to approach those of the mid and posterior intestines. However, for Pb and Ni, area-specific and whole organism transport rates were greatest in the mid (Pb) and posterior (Ni) intestines. Surprisingly, total transport rates did not differ appreciably among the essential and non-essential metals, varying only from 0.025 (Ag) to 0.050 nmol g(-1)h(-1) (Ni), suggesting that a single rate constant can be applied for risk assessment purposes. These rates were generally comparable to previously reported uptake rates from waterborne exposures conducted at concentrations 1-4 orders of magnitude lower, indicating that both routes are likely important, and that gut transporters operate with much lower affinity than gill transporters. Except for Ni, more metal was bound to mucus and/or trapped in the mucosal epithelium than was transported into the blood space in every compartment except the anterior intestine, where net transport predominated. Overall, mucus binding was a significant predictor of net transport rate for every metal except Cd, and the strongest relationship was seen for Pb.

Mercury accumulation and elimination by Eurythoe complanata were evaluated through two laboratory bioassays in the absence (bioassay A) and presence (bioassay B) of sediment. Ten individuals per treatment (three replicates) were exposed to Hg in solution (0, 1.5, 1.7, 3, 7.4, 8.7, 9, and 11 microg/L) for an 8-day exposure period. At the beginning of the elimination period, the solutions (both bioassays) and sediments (bioassay B) were replaced by seawater only and clean sediment, respectively. This period lasted 8 days. The effect of Hg concentrations on Hg accumulation by worms from bioassay A was confirmed by the Kruskal-Wallis test (H = 19.43, df = 7, chi(2) = 18.475, p = 0.01), whereas this effect was nonsignificant for bioassay B. Specimens from bioassay A accumulated about double the Hg than those of bioassay B. This indicates that sediment plays an important role in the bioaccumulation process. Mercury elimination was observed only on specimens from bioassay B, where 25% to 36% of the total Hg was eliminated during 8 days. This suggests that worms need a longer period of time to completely depurate the accumulated Hg. The Hg balance was performed at the beginning and end of the experimental periods. The total Hg percentage per aquarium decreased at the end of the experiment, which suggests that a considerable amount of Hg was evaporated or adhered to the aquarium walls. This first approach points out that experimental studies using E. complanata as a test species can be useful to evaluate the potential risk produced by Hg or other toxicants on marine biota inhabiting zones subjected to anthropogenic activities.

Adult Northern bobwhite quail (Colinus virginianus) were exposed via food to octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), an energetic compound found in soils at military training installations. Depuration of HMX into eggs was examined in an initial study, and effects on egg production, hatching, growth, development, and survival of chicks were examined in a follow-up study. HMX was readily and rapidly transferred from female quail into eggs. Marked weight loss was observed in quail exposed to 125 and 250 mg/kg HMX in food, likely due to reductions in food intake rather than a toxic mechanism. In the second study, significant alterations in body mass occurred among quail at concentrations >52.5 +/- 9.3 mg/kg but not at 12.3 +/- 1.1 mg/kg in food. Treatment-related reductions in food consumption and decreases in egg laying rates were observed. No HMX-related effects were found in chick growth or survival. Quail inhabiting HMX-contaminated sites could possibly be exposed to HMX and therefore deposition of HMX into eggs is also possible. However, results of these studies further suggest that the potential for reproductive toxicity of HMX to birds is low.

In the present work, the biosorption of radioactive thorium was investigated using a dry biomass of Sargassum filipendula as the biosorbent material. Radioactive solutions containing between 2.0 and 500.0 microg thorium were tested by biosorption with S. filipendula, yielding uptake capacities from 20 to 100%, depending on the concentration of the solution. Kinetic studies indicated that equilibrium between the thorium solution and the solid fraction was achieved after three hours of contact and that a second-order model could express the equilibrium kinetics. In order to investigate the maximum biosorption capacity of the biomass an isotherm was done, based on the experimental data, which revealed the maximum uptake capacity to be 2.59 micromol thorium/g biomass. The experimental data fitted well to a Langmuir model, which provided a good correlation between the experimental and predicted thorium uptake values.

The aim of this work is to develop the ammonia models that could be used for model predictive control (MPC) of nitrification process in a wastewater treatment plant. First, a reduced nonlinear model is presented, which is based on expression for nitrification reaction rate in activated sludge model No. 1 and modified for attached biomass processes, while second, a linear black-box model is shown. The data used for model identification were collected during several weeks of experiments on a real plant so that good identification data were obtained. The designed models were validated based on open loop simulations and predictions. Validation results show that the reduced nonlinear model performs better compared to the linear model, however, both models show relatively large errors compared to the real plant data. Hence, a closed loop simulation study was performed to see the differences between the performance of model predictive controller using previously estimated linear and nonlinear models and a standard proportional integral (PI) controller. From the simulation study results it was seen that in spite of relatively large model errors the MPC algorithms give better results in terms of ammonia removal compared to the PI controller, while MPC with the nonlinear model shows additional improvements over the MPC with the linear model.

In acidified aluminium (Al) rich freshwater positively charged Al-species (Al(i)) are the key toxic components due to the accumulation in fish gills. As a countermeasure, liming is used to increase the pH and reduce the concentration of Al(i)-species; in particular low molecular mass (LMM) Al(i)-species by hydrolyses. However, very toxic high molecular mass (HMM) Al polymers can form in the unstable mixing zone immediately after liming. In the present work gill reactivity of LMM and HMM Al-species was studied under controlled conditions in eight channel-tank mixing zone systems in the field where Atlantic salmon (Salmo salar L.) kept in cages were exposed to defined mixing zone water. Mixing zones were created by continually liming acid river water (pH 5.0-5.7) high in LMM Al(i) to pH 6.0 and 6.4, respectively. Transformation processes affecting the Al-speciation as a function of time after liming were documented by in situ hollow fibre ultrafiltration interfaced with ion chromatography, while the Al accumulation in fish gills was used as bioindicator. For fish exposed to mixing zone water immediately after liming (1 min) the Al accumulation in gills (mug Al g(-1)) was higher (factor of 2) than for fish exposed to acid water prior to liming, due to the formation of gill reactive HMM Al(i)-species. The Al accumulation in gills followed a first order kinetic expression reaching steady-state conditions after 24-h exposures. The deposition rate of Al in gills (mug Al g(-1) h(-1)) correlated with the water concentrations of HMM Al(i) (R(2)=0.80) in the mixing zones, and for LMM Al(i) in the acid water (R(2)=0.92). Due to the transient nature of HMM Al(i) the deposition rate of Al decreased from the point of liming with a factor of 10 downstream the channel-tank system (i.e. 100 min after liming). The concentration of gill accumulated Al was higher (factor of 3) immediately after high level liming (pH 6.4) than following low level liming (pH 6.0). However, high level liming was more efficient in detoxifying Al in downstream waters. Furthermore, the bioavailability of a given LMM Al(i) concentration as well as bioreactivity following liming was dependent on the TOC and silicon concentration in the acid water. Increased concentration of TOC (1.5 to 4.3 mg l(-1)) and silicon (0.3 to 1.0 mg l(-1)) reduced the gill reactivity of Al(i) by approximately 50%.

Hydrothermal ecosystems of the Mid Atlantic Ridge (MAR) are dominated by shrimps and mussels that are naturally exposed to elevated levels of heavy metals providing unique in situ laboratories for ecotoxicological investigations. This study reports on the tissue compartmentalization of both micro-essential (Fe, Zn, Cu) and toxic metals (Hg) in two nutritionally distinct cariddean vent shrimps: Rimicaris exoculata and Mirocaris fortunata, in order to shed light on organism-biota interactions at hydrothermal vents. High metal concentrations in shrimps confirmed extreme exposure levels at both geochemically different hydrothermal vents (Rainbow and Lucky Strike). However, Hg concentrations were below those reported in species for human consumption that may either suggest low bioavailability of the metal, or its effective detoxification/depuration by the hydrothermal shrimp that needs to be confirmed by post-capture toxicological investigations. Distribution of metals in different tissues had very similar patterns in both shrimp species, the target organs being gill and pylorus. Tissue levels correlated well with end-member fluid composition with regard to element ratios, i.e. Fe/Zn and Fe/Cu ratios in end-member fluids reported for Rainbow and L. Strike were conserved in the gills of M. fortunata. Moreover, R. exoculata that lives closer to venting exits as compared to M. fortunata, had similar or often less metals accumulated in selected organs, possibly owing to its higher degree of adaptation to hydrothermal conditions. Despite of high concentrations in tissues micro essential metals only represented a small fraction (14-36%) of the whole body burden indicating preponderance of minerals on the surface and/or in the gut, and thus points to improper use of whole body concentration in metal bioavailability interpretations at hydrothermal vents.

Bio-monitoring of some heavy metal levels (Cd, Pb, Zn, Cu) in whole edible soft parts of Mytilus galloprovincialis (L. 1758) was conducted in Turkish Aegean Sea coast during the period of September 2002-August 2003 seasonally. Moreover, some physico-chemical environmental parameters, also have been analysed in the same region. The values of some physico-chemical environmental parameters in coastal waters of Turkish Aegean Sea were changed between; 9.0-27.0 ( composite function)C for temperature, 31.93-40.45 psu for salinity, 7.35-8.48 for pH and 4.05-9.50 mg/l for dissolved oxygen. The levels of trace elements in whole edible soft parts including interstitial fluids of Mediterranean mussels M. galloprovincialis (L. 1758), sampled from 6 different regions of Turkish Aegean Sea coast have ranged between; 0.04-0.52 microg Cd/g wet weight, 0.49-1.72 microg Pb/g w.w., 0.95-1.85 Cu/g w.w., 16.11-37.15 microg Zn/g w.w. The highest values for all trace metals (Cd, Pb, Zn, Cu) were measured in inner part of Izmir Bay (station 3) and lowest in Sigacik and Gulluk Bay (station 5, 6). Generally heavy metal levels are lower than the results in soft mussel tissues reported from Mediterranean regions.

We measured the relative importance of water and food as sources of the trace elements As, Cd, Co, Cu, Pb, and Zn for larvae of the benthic insect Sialis velata. To achieve this end, we first exposed its prey, the midge Chironomus riparius, to trace elements in a contaminated lake located near a nonferrous metal smelter in northwestern Quebec. Concentrations of five of the six trace elements reached a steady state in prey within one week. When predators were exposed to these contaminated prey, their trace element concentrations increased markedly for all of the trace elements studied. In contrast, exposure of S. velata to contaminated lake water led to no significant increase in their concentrations of five of the six trace elements ([Pb] increased only slightly). Additional treatments in which the predator was exposed to these trace elements in both food and water or in a combination of food and water and sediment did not lead to further increases in its contaminant concentrations beyond those measured in the food-only treatment. We conclude that food (prey) is the almost exclusive source of As, Cd, Co, Cu, and Zn for S. velata and that it is the source of 94% of its Pb. Model curves for trace element accumulation over time by the predator fit our measured data well, and trace element concentrations in food alone are sufficient to model the exchange of these contaminants in this insect.

The toxicokinetics of cadmium was determined for five populations belonging to four species of Artemia (A. salina, A. parthenogenetica, A. franciscana, and A. persimilis) using a bicompartmental model. The effects of sublethal cadmium concentration on the kinetic parameters in A. parthenogenetica were determined. The BCF values are inversely related to the concentration, as is the uptake rate (ku), whilst the elimination rate (ke) constant seems to be directly related to the exposure concentration. Values corresponding to the rate of metal influx (I) remain relatively constant (0.2477 to 0.4455 microg/g.h) in the concentration range from 0.1 to 1 mg Cd/L, and are higher (1.098 microg/g.h) at an exposure to 10 mg Cd/L. The cadmium accumulation pattern seems well conserved in the genus and is characterized by a fast elimination of the metal with Ke ranging from 0.0050 to 0.0231 h(-1). A. persimilis displays a different model to that corresponding to the other studied species exposed to the same cadmium concentration, presenting a low uptake rate constant (1.0564 mL/g. h) and a low BCF (211.3 mL/g).

Biosorption of copper by Sphaerotilus natans in different conditions of ionic strength and pH was studied by performing sorption tests in batch and membrane reactors. Equilibrium batch tests evidenced the negative effect of ionic strength and the positive effect of pH on biosorption performances: the highest determined value for copper specific uptake, q, was about 60 mg/g at pH 6 and about 15 mg/g at pH 4. A competitive equilibrium model was successfully fitted to experimental data at different ionic strength levels to account for copper-sodium competition. In membrane reactor tests, experimental profiles of copper concentration in the permeate vs. time did not evidence a significant effect of ionic strength at low pH values (4 and 5). On the other hand a more remarkable effect of ionic strength on copper concentration in the permeate was observed at pH 6. Experimental profiles of continuous biosorption in the membrane reactors were successfully simulated by developing a dynamic model accounting for Cu-Na competition and for binding ability of cells fragments.

Estuaries in urban regions present unique environmental management challenges. Ecosystems in urban estuaries are typically impacted by habitat loss and degradation, watershed modification, and nonpoint and point sources of many chemicals. Restoring such systems requires an understanding of the relative contribution of various stressors to overall ecological conditions and an understanding of shifting patterns of stress over time. In this article, we present the results of a multiparameter environmental assessment of a quintessential urbanized waterway: the lower Passaic River in the vicinity of Newark, New Jersey, USA. To provide the foundation for effective management decision making, we quantified baseline conditions (habitat losses and degradation), chemical concentrations in sediment and biota relative to published toxic effect levels, direct toxicity of sediments to benthic organisms, and food-web mediated risks to fish-eating birds. Habitat losses have been severe (greater than 85% of wetlands, nearly 100% of the total length of tidal and nontidal tributaries, and 100% of natural shoreline habitat have been lost), resulting in substantial habitat constraints on biota. Despite this, biological communities are present in the lower Passaic. In general, concentrations of toxic chemicals in surface sediments have fallen with time, and natural recovery processes are proceeding. Chemical concentrations remain high enough to impair survival of amphipods, but not amphipod growth or polychaete growth or survival as measured in laboratory bioassays using field-collected sediment. Fish and blue crab body burdens of some metals, PCBs, and the pesticide, DDT, are at concentrations sufficiently high to exceed toxicity thresholds. The resident fish-eating bird--the belted kingfisher--is at exposure risk from some metals, PCBs, and polychlorinated dibenzo-p-dioxins and dibenzo furans (PCDD/Fs). Migratory waders--the herons and egrets--are not at risk from chemical exposure. These complex findings suggest that restoring the lower Passaic River to ecological health is a correspondingly complex task. Habitat constraints must be eased for biotic components of the ecosystem, and chemical effects must be reduced for those organisms that are present. Only a coordinated, multidisciplinary restoration program will succeed in this challenging environment.

Mollusks living in seas can accumulate heavy metals, and may serve as excellent passive biomonitors. During a period of 1 year, bioaccumulation of As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn was examined in nine kinds of mollusks (Rapana venosa, Neverita didyma, Scapharca subcrenata, Mytilus edulis, Amusium, Crassostrea talienwhanensis, Meretix meretrix, Ruditapes philippinarum, and Mactra veneriformis), which were collected at eight coastal sites along the Chinese Bohai Sea. Metal concentrations were directly determined by inductively coupled plasma mass spectrometer (ICP-MS). Two certified reference materials, dogfish muscle (DORM-2) and mussel (GBW 08571), were used to validate the methods, and the recoveries were within 83.72-112.30% of the certified values. Bioaccumulation of metals varied strongly among sampling sites and species. Statistical analysis (one-way ANOVA) indicated that different species examined showed different bioaccumulation of metals, and perhaps they could be used as potential biomonitors to investigate the contamination levels of heavy metals. Principal component analysis (PCA) and correlation analysis were used to study the relationships between these heavy metals. The results showed that, in nine mollusks' tissues, there are significant correlations between these elements in adjacent main group or subgroup in periodic table of elements.

The toxic effects of Cd, Cu, and Zn on four different marine phytoplankton, Dunaliella tertiolecta, Prorocentrum minimum, Synechococcus sp., and Thalassiosira weissflogii, were examined by comparing the cell-specific growth rate, pulse-amplitude-modulated (PAM) parameters (maximum photosystem II quantum yield phiM and operational quantum yield phi'M, chlorophyll a content, and cellular metal concentration, over a 96-h period. The calculated no-observed-effect concentration (NOEC) based on both cell-specific growth rate and two PAM parameters (phiM and phi'M) were mostly identical. Thus, these PAM parameters and cell-specific growth rate were comparable in their sensitivities as the biomarkers for trace metal toxicity to marine phytoplankton. The cyanobacteria Synechococcus sp. was the most sensitive species among the four algal species tested because of its higher cell surface to volume ratio. The toxicity of the three tested metals followed the order of Cd > Cu > Zn based on the cellular metal concentration of the four algae at the NOEC. The cellular metal bioaccumulation followed the same Freundlich isotherm for each metal regardless of the algal species, indicating that the metal accumulation was a nonmetabolic process under high ambient metal concentrations and that the cell surface metal binding was comparable among the different species. For all the algae examined in our study, the bioaccumulation potentials of Cu and Zn were similar to each other, while the Cd bioaccumulation was much lower under environmentally realistic metal concentration.

The toxicity of As(V) and As(III) to two axenic tropical freshwater microalgae, Chlorella sp. and Monoraphidium arcuatum, was determined using 72-h growth rate-inhibition bioassays. Both organisms were tolerant to As(III) (72-h concentration to cause 50% inhibition of growth rate [IC50], of 25 and 15 mg As[III]/L, respectively). Chlorella sp. also was tolerant to As(V) with no effect on growth rate over 72 h at concentrations up to 0.8 mg/L (72-h IC50 of 25 mg As[V]/L). Monoraphidium arcuatum was more sensitive to As(V) (72-h IC50 of 0.25 mg As[V]/L). An increase in phosphate in the growth medium (0.15-1.5 mg PO4(3-)/L) decreased toxicity, i.e., the 72-h IC50 value for M. arcuatum increased from 0.25 mg As(V)/L to 4.5 mg As(V)/L, while extracellular As and intracellular As decreased, indicating competition between arsenate and phosphate for cellular uptake. Both microalgae reduced As(V) to As(III) in the cell, with further biological transformation to methylated species (monomethyl arsonic acid and dimethyl arsinic acid) and phosphate arsenoriboside. Less than 0.01% of added As(V) was incorporated into algal cells, suggesting that bioaccumulation and subsequent methylation was not the primary mode of detoxification. When exposed to As(V), both species reduced As(V) to As(III); however, only M. arcuatum excreted As(III) into solution. Intracellular arsenic reduction may be coupled to thiol oxidation in both species. Arsenic toxicity most likely was due to arsenite accumulation in the cell, when the ability to excrete and/or methylate arsenite was overwhelmed at high arsenic concentrations. Arsenite may bind to intracellular thiols, such as glutathione, potentially disrupting the ratio of reduced to oxidized glutathione and, consequently, inhibiting cell division.

Coupled respirometric and radiotracer techniques were applied to simultaneously measure the rates of oxygen and metal uptake in the green mussel Perna viridis. This was performed under different metabolic conditions by varying the ambient oxygen partial pressure (P(O2)), temperature, air exposure, and body size. When the mussels were tested under different hypoxic and anoxic conditions, Cd and Zn uptake decreased with decreasing P(O2), accompanied by a decrease in the ventilation activity of mussels. Significant reduction in metal uptake was observed at a P(O2) level of 3 kPa. Under anoxic conditions, the uptake of Cd and Zn was 1.6 to 2.7 times and 2.8 times, respectively, lower than those measured under normoxia. In contrast, both the absorption efficiencies of Cd and Zn and the oxygen extraction efficiency increased significantly with decreasing P(O2). There were significant correlations between the rates of Cd/Zn and O2 uptake by the mussels when quantified under various P(O2) levels. The uptake of Cd and Zn was temperature dependent and increased with temperature over a range of 15 to 30 degrees C. Significant correlations between the rates of Cd/Zn and O2 uptake were also found in the temperature experiments. With reimmersion of mussels after aerial exposure, the mussels experienced an apparent O2 debt. Metal uptake also increased within the first 15 min followed by gradual recovery to the control levels. Similarly, the quantified uptake rates of Zn were significantly correlated with the O2 uptake in experiments with different sizes of mussels. These results strongly suggest that Cd and Zn uptake are coupled with oxygen uptake in the mussels; thus, physiological processes need to be considered in studying metal accumulation.

This study was undertaken to improve the understanding of arsenic species and their pathways of formation in marine animals: fish (Odax cyanomelas), abalone (Haliotis rubra), and sea urchins (Heliocidaris erythrogramma and Centrostephanus rodgersii) that are directly exposed through their diets to dimethyl arsenoriboses in macroalgae (Phyllospora comosa and Halopteris platycena). The identification of dimethyl arsenoriboses (phosphate, sulfonate, and glycerol) in both dominant macroalgae species, and especially digestive tissues of marine animals that consume them, suggests these arsenic species, are to some degree accumulated directly from their diets without degradation or conversion. An unknown arsenic species in H. rubra intestinal tissue was identified using tandem mass spectrometry as 2',3'-dihydroxypropyl 5-deoxy-5-trimethyl arsonioriboside (trimethyl glycerol arsenoribose). The concentration of trimethyl glycerol arsenoribose in H. rubra intestinal tissue was estimated to account for 28% (5.0 microg g(-1) dry mass) of the methanol-water-soluble arsenic fraction. The presence of a trimethyl glycerol arsenoribose in marine animal tissues may be due to microbial-mediated processes that promote the reduction and methylation of dimethyl arsenoriboses released during the breakdown of macroalgae in their diets. Arsenobetaine formation may then occur in the lumen of the digestive tract (i.e., mediated by microorganisms) or in the liver catalyzed by enzymes. The identification of a large amount of trimethyl glycerol arsenoribose in H. rubra intestinal tissue suggests this species is a main constituent in the pathway for arsenic in this marine animal.

Deterioration in water quality caused by the movement of excessive soil P has created a condition necessary for the development of a sustainable P remediation technology. In this investigation, the phytoremediation potential of Gulf and Marshall ryegrass (Lolium multiflorum) grown in a greenhouse was determined under varying conditions of soil P concentration, pH, and temperature. Both genotypes demonstrated P accumulations > or =1% shoot dry weight depending on soil P concentrations (0-10 g of P/kg of soil), with higher shoot P in Gulf than Marshall ryegrass. An increase in plant biomass was proportional to the increasing concentrations of P up to a level of 10 g of P/kg of soil. The effect of soil pH on plant uptake of P was noticeable with a significant rise in shoot P in acidic soil (pH 5.6) as compared to soil with pH 7.8. Significant differences were observed in the biomass productivity and shoot P accumulation at varying temperatures in both grass types. The patterns of acid phosphomonoesterase and phytase activities in plant roots were interesting, activities being 2-fold higher in alkaline soil than acidic soil in both genotypes. The effect of P supply on the enzyme activity was also distinct, as plants growing in a high P concentration showed higher activity (nearly 30%) than those growing under P deficiency conditions (with no addition of P). These results indicate that Gulf and Marshall ryegrass can accumulate high P under optimal conditions and thus reduce soil P concentrations in successive cropping.

The purpose of this study was to examine relationships among water, sediment, and fish tissue metal concentrations as they relate to fish diversity, tissue metal accumulation, and fish morphometric and reproductive condition. Fish were captured in 12 lakes near Sudbury, Ontario, Canada, that ranged in their degree of metal contamination. In general, metal concentrations in water and sediment decreased with increasing distance from industrial operations. However, only Cu and Ni demonstrated this trend in sediments. Although 20 fish species were identified in the 12 lakes, only one species, yellow perch (Perca flavescens), was common to all 12 lakes. Fish diversity was only associated with sediment metals, suggesting that short-term processes are much less important than long-term processes for fish community recovery in metal-contaminated lakes. Multivariate characterization of water metal concentrations resulted in three lake clusters: Group 1 consisted of reference lakes; Group 2 lakes had high alkalinity, conductivity, hardness, pH, waterborne metals (especially Se), and sediment Cu and Ni concentrations; Group 3 lakes had high pH, waterborne and sediment Cu, and sediment Ni, intermediate alkalinity, conductivity, and waterborne metals (except Al and Fe), and low hardness and waterborne Al and Fe. Liver Cd, Cu, Ni, Pb, and Zn, muscle Zn, and intestinal Cd and Zn were highest, and muscle Cu and male gonadosomatic index (GSI) were lowest, in Group 3 fish. Liver, muscle, and intestinal Se concentrations, and Fulton's condition factor (FCF), hepatosomatic index (HSI), and male GSI were highest in Group 2 fish. Group 1 fish had the highest muscle Hg concentrations and female GSI. Muscle Se appeared to have an antagonistic effect on muscle Hg accumulation as a function of distance from smelting operations. Neither Cu nor Ni, both metals of concern in the Sudbury area, was useful for predicting fish condition, probably because of homeostatic regulatory control. Liver Cd accumulation, which was negatively related to FCF (r = -0.16; P < 0.05), exhibited strong, nonlinear inhibition (r2 = 0.99; P < 0.0001) as a function of water hardness. Because Cd was not detected in water samples in this study, we suspect that branchial Ca2+ uptake may play some role in reducing dietary Cd uptake in hard water lakes. Selenium has received relatively little attention in the contaminated systems around Sudbury, yet our results demonstrated that tissue Se was related to all condition metrics studied. Moreover, evidence was provided that suggests that there is a gender-specific interaction between dietary Se and Cu uptake that may contribute to decreased female reproductive condition in wild yellow perch.